xo 0,0,1,1

Command line tool to generate idiomatic Go code for SQL databases supporting PostgreSQL, MySQL, SQLite, Oracle, and Microsoft SQL Server

About xo

xo is a cli tool to generate Golang types and funcs based on a database schema or a custom query. xo is designed to vastly reduce the overhead/redundancy of writing (from scratch) Go types and funcs for common database tasks.

Currently, xo can generate types for tables, enums, stored procedures, and custom SQL queries for PostgreSQL, MySQL, Oracle, Microsoft SQL Server, and SQLite databases.

Additionally, support for other database abstractions (ie, views, many-to-many relationships, etc) are in varying states of completion, and will be added as soon as they are in a usable state.

Please note that xo is NOT an ORM, nor does xo generate an ORM. Instead, xo generates Go code by using database metadata to query the types and relationships within the database, and then generates representative Go types and funcs for well-defined database relationships using raw queries.

Database Support Features

The following is a matrix of the supported features for each database:

PostgreSQL MySQL Oracle Microsoft SQL Server SQLite
Models :white_check_mark: :white_check_mark: :white_check_mark: :white_check_mark: :white_check_mark:
Primary Keys :white_check_mark: :white_check_mark: :white_check_mark: :white_check_mark: :white_check_mark:
Foreign Keys :white_check_mark: :white_check_mark: :white_check_mark: :white_check_mark: :white_check_mark:
Indexes :white_check_mark: :white_check_mark: :white_check_mark: :white_check_mark: :white_check_mark:
Stored Procs :white_check_mark: :white_check_mark:
ENUM types :white_check_mark: :white_check_mark:
Custom types :white_check_mark:


Install goimports dependency (if not already installed):

go get -u golang.org/x/tools/cmd/goimports

Then, install in the usual way:

go get -u github.com/knq/xo

NOTE: Go 1.6+ is needed for installing from source, as xo makes use of the trim template syntax in Go templates, which is not compatible with previous versions of Go. However, the code generated by xo should compile with Go 1.3+.


The following is a quick working example of how to use xo:

# make an output directory
mkdir models

# generate code for a postgres schema
xo pgsql://user:[email protected]/dbname -o models

# generate code for a custom postgres query
xo pgsql://user:[email protected]/dbname -N -M -B -T AuthorResult -o models/ << ENDSQL
  a.name::varchar AS name,
  b.type::integer AS my_type
FROM authors a
  INNER JOIN authortypes b ON a.id = b.author_id
  a.id = %%authorID int%%
LIMIT %%limit int%%

# build generated code
go build ./models

Command Line

The following are xo’s arguments and options:

usage: xo [--verbose] [--schema SCHEMA] [--out OUT] [--append] [--suffix SUFFIX] [--single-file] [--package PACKAGE] [--custom-type-package CUSTOM-TYPE-PACKAGE] [--int32-type INT32-TYPE] [--uint32-type UINT32-TYPE] [--ignore-fields IGNORE-FIELDS] [--fk-mode FK-MODE] [--use-index-names] [--use-reversed-enum-const-names] [--query-mode] [--query QUERY] [--query-type QUERY-TYPE] [--query-func QUERY-FUNC] [--query-only-one] [--query-trim] [--query-strip] [--query-interpolate] [--query-type-comment QUERY-TYPE-COMMENT] [--query-func-comment QUERY-FUNC-COMMENT] [--query-delimiter QUERY-DELIMITER] [--query-fields QUERY-FIELDS] [--escape-all] [--escape-schema] [--escape-table] [--escape-column] [--enable-postgres-oids] [--name-conflict-suffix NAME-CONFLICT-SUFFIX] [--template-path TEMPLATE-PATH] DSN

positional arguments:
  dsn                    data source name

  --verbose, -v          toggle verbose
  --schema SCHEMA, -s SCHEMA
                         schema name to generate Go types for
  --out OUT, -o OUT      output path or file name
  --append, -a           append to existing files
  --suffix SUFFIX, -f SUFFIX
                         output file suffix [default: .xo.go]
  --single-file          toggle single file output
  --package PACKAGE, -p PACKAGE
                         package name used in generated Go code
                         Go package name to use for custom or unknown types
  --int32-type INT32-TYPE, -i INT32-TYPE
                         Go type to assign to integers [default: int]
  --uint32-type UINT32-TYPE, -u UINT32-TYPE
                         Go type to assign to unsigned integers [default: uint]
  --ignore-fields IGNORE-FIELDS
                         fields to exclude from the generated Go code types
  --fk-mode FK-MODE, -k FK-MODE
                         sets mode for naming foreign key funcs in generated Go code [values: <smart|parent|field|key>] [default: smart] [default: 0xc8200f0500]
  --use-index-names, -j
                         use index names as defined in schema for generated Go code
  --use-reversed-enum-const-names, -R
                         use reversed enum names for generated consts in Go code
  --query-mode, -N       enable query mode
  --query QUERY, -Q QUERY
                         query to generate Go type and func from
  --query-type QUERY-TYPE, -T QUERY-TYPE
                         query's generated Go type
  --query-func QUERY-FUNC, -F QUERY-FUNC
                         query's generated Go func name
  --query-only-one, -1   toggle query's generated Go func to return only one result
  --query-trim, -M       toggle trimming of query whitespace in generated Go code
  --query-strip, -B      toggle stripping type casts from query in generated Go code
  --query-interpolate, -I
                         toggle query interpolation in generated Go code
  --query-type-comment QUERY-TYPE-COMMENT
                         comment for query's generated Go type
  --query-func-comment QUERY-FUNC-COMMENT
                         comment for query's generated Go func
                         delimiter for query's embedded Go parameters [default: %%]
  --query-fields QUERY-FIELDS, -Z QUERY-FIELDS
                         comma separated list of field names to scan query's results to the query's associated Go type
  --escape-all, -X       escape all names in SQL queries
  --escape-schema, -z    escape schema name in SQL queries
  --escape-table, -y     escape table names in SQL queries
  --escape-column, -x    escape column names in SQL queries
                         enable postgres oids
                         suffix to append when a name conflicts with a Go variable [default: Val]
  --template-path TEMPLATE-PATH
                         user supplied template path
  --help, -h             display this help and exit

Example: End-to-End

For example, given the following PostgreSQL schema:

CREATE TABLE authors (
  name text NOT NULL DEFAULT '',
  subject text NOT NULL DEFAULT ''

CREATE INDEX authors_name_idx ON authors(name);


    author_id integer NOT NULL REFERENCES authors(author_id),
    title text NOT NULL DEFAULT '',
    booktype book_type NOT NULL DEFAULT 'FICTION',
    year integer NOT NULL DEFAULT 2000

CREATE INDEX books_title_idx ON books(title, year);

CREATE FUNCTION say_hello(text) RETURNS text AS $$
    RETURN CONCAT('hello ' || $1);
$$ LANGUAGE plpgsql;

xo will generate the following (note: this is an abbreviated copy of actual output – please see the examples directory for how the generated types and funcs are used (generated via examples/postgres/gen.sh), and see the examples/postgres/models directory for the full generated code):

// Author represents a row from public.authors.
type Author struct {
    AuthorID int    // author_id
    Isbn     string // isbn
    Name     string // name
    Subject  string // subject

// Exists determines if the Author exists in the database.
func (a *Author) Exists() bool { /* ... */ }

// Deleted provides information if the Author has been deleted from the database.
func (a *Author) Deleted() bool { /* ... */ }

// Insert inserts the Author to the database.
func (a *Author) Insert(db XODB) error { /* ... */ }

// Update updates the Author in the database.
func (a *Author) Update(db XODB) error { /* ... */ }

// Save saves the Author to the database.
func (a *Author) Save(db XODB) error { /* ... */ }

// Upsert performs an upsert for Author.
func (a *Author) Upsert(db XODB) error { /* ... */ }

// Delete deletes the Author from the database.
func (a *Author) Delete(db XODB) error { /* ... */ }

// AuthorByIsbn retrieves a row from public.authors as a Author.
// Looks up using index authors_isbn_key.
func AuthorByIsbn(db XODB, isbn string) (*Author, error) { /* ... */ }

// AuthorsByName retrieves rows from public.authors, each as a Author.
// Looks up using index authors_name_idx.
func AuthorsByName(db XODB, name string) ([]*Author, error) { /* ... */ }

// AuthorByAuthorID retrieves a row from public.authors as a Author.
// Looks up using index authors_pkey.
func AuthorByAuthorID(db XODB, authorID int) (*Author, error) { /* ... */ }

// Book represents a row from public.books.
type Book struct {
    BookID   int      // book_id
    AuthorID int      // author_id
    Title    string   // title
    Booktype BookType // booktype
    Year     int      // year

// Exists determines if the Book exists in the database.
func (b *Book) Exists() bool { /* ... */ }

// Deleted provides information if the Book has been deleted from the database.
func (b *Book) Deleted() bool { /* ... */ }

// Insert inserts the Book to the database.
func (b *Book) Insert(db XODB) error { /* ... */ }

// Update updates the Book in the database.
func (b *Book) Update(db XODB) error { /* ... */ }

// Save saves the Book to the database.
func (b *Book) Save(db XODB) error { /* ... */ }

// Upsert performs an upsert for Book.
func (b *Book) Upsert(db XODB) error { /* ... */ }

// Delete deletes the Book from the database.
func (b *Book) Delete(db XODB) error { /* ... */ }

// Book returns the Author associated with the Book's AuthorID (author_id).
func (b *Book) Author(db XODB) (*Author, error) { /* ... */ }

// BookByBookID retrieves a row from public.books as a Book.
// Looks up using index books_pkey.
func BookByBookID(db XODB, bookID int) (*Book, error) { /* ... */ }

// BooksByTitle retrieves rows from public.books, each as a Book.
// Looks up using index books_title_idx.
func BooksByTitle(db XODB, title string, year int) ([]*Book, error) { /* ... */ }

// BookType is the 'book_type' enum type.
type BookType uint16

const (
    // BookTypeFiction is the book_type for 'FICTION'.
    BookTypeFiction = BookType(1)

    // BookTypeNonfiction is the book_type for 'NONFICTION'.
    BookTypeNonfiction = BookType(2)

// String returns the string value of the BookType.
func (bt BookType) String() string { /* ... */ }

// MarshalText marshals BookType into text.
func (bt BookType) MarshalText() ([]byte, error) { /* ... */ }

// UnmarshalText unmarshals BookType from text.
func (bt *BookType) UnmarshalText(text []byte) error { /* ... */ }

// SayHello calls the stored procedure 'public.say_hello(text) text' on db.
func SayHello(db XODB, v0 string) (string, error) { /* ... */ }

// XODB is the common interface for database operations that can be used with
// types from public.
// This should work with database/sql.DB and database/sql.Tx.
type XODB interface {
    Exec(string, ...interface{}) (sql.Result, error)
    Query(string, ...interface{}) (*sql.Rows, error)
    QueryRow(string, ...interface{}) *sql.Row

Example: Ignoring Fields

Sometimes you may wish to have the database manage the values of columns instead of having them managed in the generated Go code. If you are generating the Go code from an existing database, you can use the --ignore-fields flag to specify that the fields should not be managed by xo.

For instance, consider this PostgreSQL schema which defines a function and trigger to set the modified_at column automatically on UPDATE (as well as defaulting the created_at column to now() when the row is first created):

  created_at timestamptz default now(),
  modified_at timestamptz default now(),

CREATE OR REPLACE FUNCTION update_modified_column()
    NEW.modfified_at = now();
$$ language 'plpgsql';

CREATE TRIGGER update_users_modtime BEFORE UPDATE ON users FROM EACH ROW EXECUTE PROCEDURE update_modified_column();

We could ensure that these columns are managed by PostgreSQL and not by the generated Go code using --ignore-fields:

$ xo pgsql://user:[email protected]/db -o models --ignore-fields created_at modified_at

Example: Adding Methods With Custom Templates

The Go code rendered by xo is customizable using the --template-path flag. Notice that in this source repo, templates/ points towards a default selection of templates which you might be able to use to customize the templated code to your needs. You can vendor these templates into your own project to do so. e.g.:

$ mkdir templates
$ cp -r "$GOPATH/go/src/github.com/knq/xo/templates" .
$ xo pgsql://user:[email protected]/db -o models --template-path templates

The outermost template file for a generated struct is in templates/$DBTYPE.type.go.tpl. This is an excellent place to add a new method for all generated structs to have. For instance, if we have a timestamp field created_at (such as the one managed by Postgres above) we can ensure that our generated structs have a query which returns the N (or less) most recent entries in a table by adding this template:

// MostRecent will return N rows from the table sorted by recency ('created_at'
// field).
func {{ .Name }}MostRecent (db XODB, n int) ([]*{{ .Name}}, error) {
    recent := fmt.Sprintf(`SELECT {{ colnames .Fields "created_at" "modified_at" }} FROM {{ $table }} ORDER BY created_at DESC LIMIT %d`, n)
    q, err := db.Query(recent)
    if err != nil {
        return nil, err
    defer q.Close()

    // load results
    res := []*{{ .Name }}{}
    for q.Next() {
        {{ $short }} := {{ .Name }}{}

        // scan
        err = q.Scan({{ fieldnames .Fields (print "&" $short) }})
        if err != nil {
            return nil, err

        res = append(res, &{{ $short }})

    return res, nil

Note that the context (.) in the template can be divined from the source code of xo, e.g. at the time of writing, . represents an instance of Type from github.com/knq/xo/internal/types.go.

You may want to consider deleting the templates for databases other than the one you are using, as well as the generated templates/tpls.go “binary” file, from a vendored templates/ directory. Those are needed by xo upstream, but are most likely not needed for your project.

Oracle Support

Oracle support is disabled by default as the Go driver for it relies on the Oracle client libs that may not be installed on your system. If you would like to build a version of xo with Oracle support, please first install rana’s Oracle driver.

On Ubuntu/Debian, you may download the instantclient RPMs available from here. You should then be able to do the following:

# install alien, if not already installed
sudo aptitude install alien

# install the instantclient RPMs
alien -i oracle-instantclient-12.1-basic-*.rpm
alien -i oracle-instantclient-12.1-devel-*.rpm
alien -i oracle-instantclient-12.1-sqlplus-*.rpm

# get xo, if not done already
go get -u github.com/knq/xo

# copy oci8.pc from xo contrib to pkg-config directory
sudo cp $GOPATH/src/github.com/knq/xo/contrib/oci8.pc /usr/lib/pkgconfig/

# export cgo flags (rana's ora driver does not have a cgo pkg-config tag [yet])
export CGO_CFLAGS=$(pkg-config --cflags oci8)
export CGO_LDFLAGS=$(pkg-config --libs oci8)

# install rana's ora driver -- see here: https://github.com/rana/ora
go get -u gopkg.in/rana/ora.v3

# install xo with oracle support enabled
go install -tags oracle github.com/knq/xo

Design, Origin, Philosophy, and History

xo can likely get you 99% “of the way there” on medium or large database schemas and 100% of the way there for small or trivial database schemas. In short, xo is a great launching point for developing standardized packages for standard database abstractions/relationships, and xo’s most common use-case is indeed in a code generation pipeline, ala stringer.

NOTE: While the code generated by xo is production quality, it is not the goal, nor the intention for xo to be a “silver bullet,” nor to completely eliminate the manual authoring of SQL / Go code.

xo was originally developed while migrating a “large” application written in PHP to Go. The schema in use in the original app, while well designed, had become inconsistent over multiple iterations/generations, mainly due to different naming styles adopted by various developers/database admins over the preceding years. Additionally, some components had been written in different languages (Ruby, Java) and had also accumulated significant drift from the original application and schema. Simultaneously, a large amount of growth meant that the PHP/Ruby code could no longer efficiently serve the traffic volumes.

In late 2014/early 2015, a decision was made to unify and strip out certain backend services and to fully isolate the API from the original application, allowing the various components to instead speak to a common API layer instead of directly to the database, and to build that service layer in Go.

However, unraveling the old PHP/Ruby/Java code became a relatively large headache as the code, the database, and the API, had all experienced significant drift, and thus underlying function names, fields, and API methods no longer aligned. As such, after a round of standardizing names, dropping accumulated cruft, and adding a small number of relationship changes to the schema, the various codebases were fixed to match the schema changes. After that was determined to be a success, the next target was to rewrite the backend services in Go.

In order to keep a similar and consistent workflow for the developers, the previous code generator (written in PHP and Twig templates) was modified to generate Go code. Additionally, at this time, but tangential to the story here, the API definitions were ported from JSON to Protobuf to make use of its code generation abilities as well.

xo is the open source version of that code generation tool, and is the the fruits of those development efforts. It is hoped that others will be able to use and expand xo to support other databases, SQL or otherwise, and that xo can become a common tool in any Go developer’s toolbox.

Part of xo’s goal is to avoid writing an ORM, or an ORM-like in Go, and to instead generate static, type-safe, fast, and idiomatic Go code. Additionally, the xo developers are of the opinion that relational databases should have proper, well-designed relationships and all the related definitions should reside within the database schema itself – call it “self-documenting” schema. xo is an end to that pursuit.

Similar Projects

The following projects work with similar concepts as xo:

Go Generators

Go ORM-likes


  • Add (finish) stored proc support for Oracle + Microsoft SQL Server
  • Better standardize example gen.sh scripts, using usql tool
  • v1 release + binary packages for Linux, OSX, Windows
  • Unit tests / code coverage / continuous builds for binary package releases
  • Move database introspection to separate package for reuse by other Go packages
  • Overhaul/standardize type parsing
  • Finish support for –{incl, excl}[ude] types
  • Write/publish template set for protobuf
  • Add support for generating models for other languages
  • Finish many-to-many and link table support
  • Finish example and code for generated *Slice types
  • Add example for many-to-many relationships and link tables
  • Add support for supplying a file (ie, *.sql) for query generation
  • Add support for full text types (tsvector, tsquery on PostgreSQL)
  • Finish COMMENT support for PostgreSQL/MySQL and update templates accordingly.
  • Add support for JSON types (json, jsonb on PostgreSQL, json on MySQL)
  • Add support for GIN index queries (PostgreSQL)
  • Add ability to read *.sql files with ‘markup’ to parse multiple queries (a la migration scripts) [is this even necessary?]

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